Lichenoid dermatitis in paraneoplastic pemphigus - A pathogenic trigger ofepitope spreading?

Background: In select cases, lichen planus has been observed to be a parane oplastic condition sometimes associated with paraneoplastic pemphigus, a di sease featuring autoantibodies directed against plakin proteins, desmoglein s 3 and 1, and a still uncharacterized 170-kd antigen. Epitope spreading de scribes the phenomenon where underlying chronic inflammation leads to the s equential recognition of new epitopes on self-proteins over time. Observations: Five of 6 patients diagnosed as having paraneoplastic pemphig us had concomitant clinical and histological features of lichen planus. In 1 patient, re suits of the initial indirect immunofluorescence on rat bladd er were negative and only 2 of the 5 antigens were identified by immunoprec ipitation. After 1 year of worsening disease, repeated testing confirmed th e presence of antibodies directed against all 6 of the implicated antigens, supportive of our hypothesis that epitope spreading may occur in paraneopl astic pemphigus. Conclusions: Lichenoid eruptions may predispose to an early evolutionary st age of paraneoplastic pemphigus. Cell-mediated autoimmunity at the dermoepi dermal junction may promote the exposure of self-antigens and the developme nt of subsequent and progressive humoral autoimmunity. As such, paraneoplas tic pemphigus may demonstrate epitope spreading in a human, humoral-mediate d autoimmune disease.